Electron transfer-driven single and multi-enzyme biofuel cells for self-powering and energy bioscience

Amongst all the bioelectrochemical system, single enzyme fuel cells have certain unique features and capability of degrading organics and generate electricity under a low applied voltage simultaneously. Intramolecular electron transfer within a single enzyme molecule is an alternative route for electricity generation in which case, electron tunneling, and decoupling of semi-redox processes sets the resulting power output by bioelectrodes. The electricity harvesting has been successfully performed by decoupling of the redox reactions within a single type of enzyme. This review discusses and illustrates on how the bioelectrode fabrication, enzyme conformation on the electrode surface, electrode surface modification influences the power density and electron transport mechanism. We have described how energy generation pathways depend on parameters such as current density, electron transport mechanism, and enzyme conformation. The advanced applications of enzymatic biofuel cells (EBFCs) for waste-water treatment, carbon capture, and energy storage bio-solar power, and biosensing were discussed. We have also emphasized how EBFC contributes to self-powering of modern biosensors. A discussion on multi-enzyme biofuel cell was included for explaining deep oxidation and comparison with single-enzyme EBFC. Finally, this article also depicts immediate challenges for self-powering of EBFCs.